1. Field of the Invention
This invention relates in general to the manufacture of storage disks used in the computer field, and more particularly to a method for controlling a burnish cycle to minimize cycle time.
2. Description of Related Art
Hard disks are used to store information, typically coded information, utilized for data processing. An advantage of such a disk is that it can provide high-speed random access to data stored thereon. Information may be read from or written to any selected area on the memory surface of such a disk. The reading or writing of data may be performed without having to serially search the full contents of the disk to have access to a selected memory location. Generally, a hard disk is mounted with a disk drive, which includes a motor for rotating the hard disk and an actuator for moving a transducer relative to the surface of the rotating hard disk to provide access to circumferential tracks on the hard disk. A plurality of disks may be mounted on a single spindle in spaced relationship to one another and transducers are provided to interact with opposite planar surfaces of each of the disks.
The disks are typically magnetic disks, which include a magnetic surface for recording information thereon. Moreover, the heads that interact with each of the surfaces are referred to as “flying heads.” Thus, the flying heads do not touch the surface of the disk during the rotation of the disk. Instead, the flying heads ride on an air bearing that is created between the slider and the disk. The air bearing prevents wear of either the head or the disk surface by reducing or eliminating contacts as the head and the disk surface experience relative movement. Wear of the disk surface due to contact results in the loss of information stored on the magnetic disk.
The transducer head is typically in the form of a magnetoresistive (MR) head or element carried on a slider body. Oftentimes, the slider and transducer are designated as a “head.” Regardless, the slider body is mounted to a flexible suspension portion of an arm assembly that is otherwise part of the actuator assembly. Upon final assembly, the actuator assembly positions the slider over a surface of a disk. The slider is configured such that as the disk rotates, an air bearing develops between the slider and the disk surface causing the slider, and thus the read and write elements, to lift and fly several micro inches above the disk surface. The distance between the slider and the disk surface is often times referred to as a “fly height.” In magnetic recording technology it is desired to “fly” the slider as closely as possible to the disk surface (i.e., minimal fly height) so that the read transducer can distinguish between the magnetic fields emanating from closely spaced regions on the disk.
Disk drive manufacturers constantly strive to improve upon the slider design to provide a minimized fly height, along with satisfying other constraints as slider roll, pitch, and skew. These features are typically accomplished by forming (e.g., etching) aerodynamic rails or pads into the slider body. These rails must be machined to exacting standards, and constitute permanent structures. That is to say, the rails or pads will not erode or otherwise change shape upon expected or unexpected contact with the disk surface. In contrast, a recently developed slider configuration incorporates a burnishable slider air bearing surface (ABS). Unlike traditional slider rail or pad constructions, a burnishable slider design relies upon reshaping of the slider ABS upon contact with the rotating disk to achieve a final shape and fly height.
As a point of reference, the body of a burnishable slider is formed to have generally linear or planar side and bottom surfaces, but the ABS may have an enlarged height or thickness. More particularly, in conjunction with other disk drive parameters, including configuration of the actuator arms and other slider components, such as a slider body support structure, the slider ABS is normally formed to a thickness slightly greater than the expected final thickness that would otherwise produce a desired fly height. In other words, upon final assembly of the disk drive and initial rotation of the disk at normal operation speeds, the slider continues to contact or rub against the relevant disk surface. Because the slider ABS is made of a burnishable material, continued contact between the slider and the rotating disk burnishes the slider, thereby reducing its height. In theory, this burnishing procedure continues until the slider thickness has been reduced to a point where slider just begins to fly relative to the disk surface. This results in fly height that theoretically is as small as possible.
The above-described burnishable slider design appears highly viable. The exacting manufacturing tolerances required of conventional slider pad or rail designs is eliminated, and a highly minimized fly height can be achieved. However, opportunities for improvement exist. The current technique for burnishing the slider produces a slider height profile that is essentially co-planar with the disk surface. For disk drive applications, this shape is less than aerodynamically optimal. Burnishable slider technology represents a distinct advancement in the disk drive art. Certain opportunities exist for perfecting implementation of this technology, including an optimal burnishment methodology.
It can be seen that there is a need for a method for controlling a burnish cycle to minimize cycle time.